Severe shortages of donor organs limit the use of orthotopic liver transplantation (LT), the only proven therapy for end-stage liver diseases. Primary non-function (PNF) of liver grafts after transplantation typically results in recipient death or necessitates retransplantation, which further exacerbates the shortage of donor livers. Unfortunately, effective therapies for PNF are not yet known. Liver ischemia/reperfusion (IR) injury plays an essential role in initial poor graft function and PNF. Our recent exciting observations indicate that inhibition of sphingosine kinase (SK) dramatically decreases PNF after hepatic warm IR in vivo, suggesting that sphingolipids may be key regulators of IR injury. In particular, SK is a critical regulator of inflammatory cells that are of central importance in IR injury. Our data also show that the SK inhibitor blocks mitochondrial dysfunction induced by IR, a major mechanism of cell death. Therefore, we hypothesize that SK is a key molecular target for the development of new drugs to prevent and/or treat PNF after LT. We have recently identified novel inhibitors of SK that more potent than any other known SK inhibitor, while being of high specificity and low toxicity. We hypothesize that these SK inhibitors can be used to attenuate IR-induced liver injury and thereby improve the outcome of LT. Therefore, we will conduct the following studies during Phase I of this STTR project: Specific Aim 1. To synthesize sufficient amounts of SK inhibitor ABC294640 for in vivo studies, characterize its solubility and stability in cold storage solution and determine its penetration into liver in vivo and explants during cold storage. Specific Aim 2. To determine the effects of ABC294640 in lean liver transplantation and investigate the mechanisms of protection. Specific Aim 3. To determine the effects of ABC294640 in fatty liver transplantation. Taken together, inhibitors of SK represent a novel approach toward the identification of new anti-IR injury drugs. We will use a rat orthotopic LT model in combination with state-of-the-art intravital multiphoton microscopy and molecular biology techniques to evaluate the clinical potential of a lead SK inhibitor as a new therapy that can be taken to the clinic to improve the outcome of LT. PUBLIC HEALTH RELEVANCE: Use of live-saving liver transplantation techniques is limited by a severe shortage of usable donor livers, resulting in the deaths of patients on recipient waiting lists. Ischemia-reperfusion injury plays an essential role in the initial poor function and consequent failure of many liver grafts. Accumulating information suggests a role for sphingosine kinase (SK) activity in hepatotoxicity following ischemia, and our Preliminary Studies indicate that this can be dramatically improved by an SK inhibitor. The proposed studies will determine if this compound has potential for further development as a hepatoprotective drug for liver transplantation.